Ask most Ontario employers what the law requires on workplace mental health and you get one of two answers. Either "nothing, that is a wellness thing," or "everything, we have to have a whole program." Both are wrong, and the reason they are wrong is that the legal duties do not live in one place. They are spread across three different laws, and each one does a different job.
Let's map all three, because you cannot manage a duty you cannot see. Your obligations come from OHSA, from the workers' compensation system, and from human rights law. Miss any one and you have a gap.
One: OHSA — The Duties You Must Build
The Occupational Health and Safety Act is where your active, build-it-now duties live, and they are narrower than people think. OHSA does not require a broad "mental health program." It requires you to manage two specific psychological hazards: workplace violence and workplace harassment, under Part III.0.1.
Here is what that actually means:
- Section 32.0.1 requires written policies on workplace violence and workplace harassment, reviewed at least once a year. If you regularly employ six or more workers, the policies must be posted where workers will see them.
- Section 32.0.2 requires a real workplace violence program, not just a policy. It must include measures to control the risks, procedures to report incidents, and procedures to summon immediate help.
- Section 32.0.3 requires you to assess the risk of workplace violence arising from the nature of the work and the conditions of work, and to share the results with your joint health and safety committee or representative.
- Section 32.0.6 requires a written workplace harassment program, developed with your joint health and safety committee, covering how complaints are reported, investigated, and communicated, including when the person complained about is the employer or a supervisor.
- Section 32.0.7 requires that harassment complaints are actually investigated, and that both the complainant and the respondent get written notice of the results and any corrective action.
There is also section 25(2)(h), the general duty clause, requiring an employer to "take every precaution reasonable in the circumstances for the protection of a worker." It is a real duty, but it is a floor, not a program spec. It does not tell you what a compliant mental health program looks like. The violence and harassment sections do, and those are where a Ministry inspector will actually check.
Notice the limit. OHSA reaches violence and harassment. It does not require you to manage workload, job design, or chronic stress. That is a deliberate gap, and the next two laws are where the consequences of that gap show up.
Two: WSIB — The Liability You Must Cover
This is the piece employers miss most often, because it is not a "build a program" duty. It is a compensation exposure, and it changed the game in 2018.
As of January 1, 2018, through Bill 127, the Stronger, Healthier Ontario Act, Ontario amended section 13 of the Workplace Safety and Insurance Act so that workers can claim WSIB benefits for chronic and traumatic mental stress arising out of and in the course of employment. Before that, mental stress claims were largely limited to sudden, traumatic events. Now chronic mental stress is covered.
A worker with a chronic mental stress claim, with an accident date on or after January 1, 2018, has to meet three conditions: a diagnosis from a regulated health professional based on the DSM, a substantial work-related stressor such as workplace bullying or harassment, and that stressor being the predominant cause of the diagnosed condition.
Here is why this matters even though it is not a program you build. It means the psychological hazards OHSA does not require you to manage, workload, toxic supervision, unaddressed harassment, can still land as compensable claims that hit your WSIB experience rating. The law stopped requiring you to only prevent violence and harassment and started making you pay for chronic stress you let build. Prevention is no longer just good practice. It is loss control.
Three: The Human Rights Code — The Duty to Accommodate
The third law operates on the individual level. Under the Ontario Human Rights Code, mental disability is a protected ground, and employers have a duty to accommodate a worker's mental health disability to the point of undue hardship.
In plain terms: when a worker has a mental health condition that affects their work, you cannot simply discipline or dismiss your way out of it. You have a legal duty to explore accommodation, modified duties, adjusted timelines, time off for treatment, whatever is reasonable short of genuine undue hardship on your operation. This duty is triggered by the individual situation, not by your headcount or your program. It applies whether you have six workers or six hundred.
This is the law that turns a mental health issue from an HR judgment call into a legal obligation. Handle it badly and you are not looking at a WSIB claim, you are looking at a human rights application.
Putting the Three Together
Here is the full picture, because no single law gives it to you.
OHSA tells you what to build: current, committee-developed violence and harassment programs, reviewed annually and actually followed. WSIB tells you what you now pay for: chronic mental stress became compensable in 2018, so the hazards OHSA does not require you to manage still carry a real dollar cost. And the Human Rights Code tells you how to treat the individual: accommodate mental disability to the point of undue hardship, every time it comes up.
CSA Z1003, the national psychological health and safety standard, sits on top of all three. It is voluntary, not law. But it is the framework that addresses the exact space between these laws, the workload, culture, and job-design hazards that OHSA does not require you to manage but WSIB will make you pay for.
So the honest answer to "what does Ontario law require on workplace mental health" is this. Build the OHSA programs, because those are enforceable and specific. Understand the WSIB exposure, because prevention is now cheaper than the claims. Know your accommodation duty, because it applies to every worker individually. Get those three right, and the voluntary standard becomes a smart next step instead of a source of confusion.
If you are not sure which of the three you have actually covered and which you have only assumed, that is the first thing worth checking, before you build anything new on top of it.
WorkSafe Sounds helps Ontario employers separate the mental health duties they must meet from the best practice they can choose. If you want a clear read on where you stand across OHSA, WSIB, and the Human Rights Code before you spend on a program, that is exactly where we start.